The markets are moved by animal spirits, and not by reason.

Well, when I get new information, I rethink my position. What, sir, do you do with new information?

A study of the history of opinion is a necessary preliminary to the emancipation of the mind.

I'd rather be vaguely right than precisely wrong.

For at least another hundred years we must pretend to ourselves and to every one that fair is foul and foul is fair; for foul is useful and fair is not. Avarice and usury and precaution must be our gods for a little longer still.

Morally and philosophically I find myself in agreement with virtually the whole of it: and not only in agreement with it, but in deeply moved agreement.

It's not bringing in the new ideas that's so hard; it's getting rid of the old ones.